The present research program involves the investigation of learning parameters and physiological mechanisms involved in the voluntary self-regulation of heart rate, and the examination of clinical applications of this biofeedback technique. This proposed program involves three interrelated lines of research: (1) The assessment of underlying physiological mechanisms and constraints of the heart-rate control learning process, and the investigation of parameters which maximize such learning and transfer of learning to no-feedback conditions. Two studies are proposed. One study assesses the effectiveness of simultaneous heart rate-blood pressure feedback training in maximizing the learned control of heart rate. The other examines the effectiveness of a feedback "fading" technique in producing maximal transfer of learning from feedback to no-feedback conditions. In both studies, a host of physiological responses will be recorded in order to assess the physiological mechanisms involved in the control-process, both early and late in training. (2) The evaluation of the clinical effectiveness of voluntary heart-rate control in modifying anxiety and depression. Two studies are proposed, one of which examines the effectiveness of this technique in reducing speech anxiety, and the other of which evaluates the application of this technique to the treatment of reactive depression. (3) The evaluation of the use of heart-rate control training procedures with cardiac patiens. A study is proposed which assesses the effects of long-term training in patients with cardiac arrhythmias. In all of the above three areas, individual differences in physiological responding and personality variables will also be examined in order to determine if they are predictive of ability to learn to voluntarily control heart rate.